Now, the emphasis is clearly on the job and the program, not on the job advertisement. Even the fact that you have written a letter can be implicitly understood. Therefore, you could use this sentence as a subject heading at the beginning of the letter.

Date:
Name:
Street address:
Phone:
E-mail:

Subject: Job openinginThe Young Professionals Program.

You could then begin by discussing your work experience, special skills, and/or personal interests.